Robberecht, R., M.M. Caldwell, and W.D. Billings. 1980. Leaf ultraviolet optical properties along a latitudinal gradient in the arctic-alpine life zone. Ecology 61:612-619.

Abstract. Leaf epidermal transmittance of terrestrial solar ultraviolet-B radiation (295-320 nm) was examined along a latitudinal gradient of solar UV-B radiation. In high UV-B radiation zones, e.g., equatorial and topical regions, mean epidermal transmittance for the species examined was less than 2%. At higher latitudes, mean epidermal transmittance exceeded 5%. Although this latitudinal solar UV-B gradient represents more than a seven-fold difference in daily integrated UV-B irradiance, the calculated mean effective UV-B irradiance at the mesophyll of low-latitude species is not substantially different from that of species at higher latitudes. Species in high UV-B radiation environments appear to attenuate this radiation more effectively than those in lower irradiance environments. In most cases, absorption of UV-B in the epidermis is the major parameter effecting low transmittance. Reflectance from glabrous leaves is generally less than 10%. In some species, pubescent or glaucous leaf surfaces can reflect more than 40% of the UV-B radiation incident on a horizontal leaf, although such surface characteristics do not necessarily indicate high UV-B reflectance. Under controlled conditions, epidermal transmittance in Pisum sativum L. decreased in response to UV-B irradiation. The modification of epidermal transmittance, resulting in lower UV-B irradiance at the mesophyll, may represent a mechanism of plant acclimation to UV-B radiation. Such acclimation may have occurred in several wildland species of temperate-latitude origin that have invaded high UV-B irradiance equatorial and tropical regions.

This research was supported by grants from the National Science Foundation (DEB-7622381) and the National Aeronautics and Space Administration (NAS-9-14871).